Maintenance lift



May 27, 1969 N. H. MILLER MAINTENANCE LIFT Sheet Filed April 19, 1967 INVENTOR. WORM/91715. M/(Z'l? Sheet 2 arz N. H. MILLER MAINTENANCE LIFT iled April 19, 1967 May 27, 1969 M R. m w 0 r, M WW 9 00 a. P L a w w fi 9 P B 5M1 "v 9 8 w M/ U F v I 0 m @flw 31H 4, 3 a 5 9 w n a a 2 6 5 ,1 f 7 6- m .QIV-////// a y w; 4. a

United States Patent O 3,446,366 MAINTENANCE LIFT Norman H. Miller, 8715 Woolworth Ave., Omaha, Nebr. 68124 Filed Apr. 19, 1967, Ser. No. 632,075 Int. Cl. 156% 3/02; B60p 1/02; 1325 5/00 U.S. Cl. 214-1 5 Claims ABSTRACT OF THE DISCLOSURE A lift provided with a mobile rectangular base structure, a vertically adjustable platform and a vertically adjustable frame with a load support thereon mounted on the base structure. The platform, which is supported by telescoping jack assemblies, has a cut-out portion adapted to receive the frame and is substantially L-shaped. The frame is rectangular and is also mounted on telescoping jack assemblies. The relative elevation of the frame and the platform can be adjusted and the .attitude and elevation of the load support relative to the frame, can be adjusted by means of four independently extensible elements which extend between the frame and the load support.

Brief description of the invention The present invention relates to a lift and more specifically, to a maintenace lift adapted to handle airplane engines and permit work on said engines while they are on the lift whether the lift be in an elevated position or in a lowered position. Of course, the lift is well suited for other tasks and the use of the lift is in no way restricted to the handling of airplane engines.

The lift comprises a rectangular base frame mounted on wheels, a substantially L-shaped platform having a cutout portion mounted on said base frame by means of telescoping hydraulic jacks, a frame, which is received within the cutout portion of the platform mounted on telescoping hydraulic jacks, and a work support mounted on the frame by means of four independently extensible elements which extend between respective corners of the frame and the work support. A control means is provided on the platform for adjusting the relative height of the platform with regard to the frame, and a control means is provided on the frame for operating the extensible elements together, in pairs, or individually, so that the work support may be adjusted with respect to the first frame both as to height and attitude.

One object of the present invention is to provide a maintenance lift with a substantially L-shaped platform wherein the worker may easily work on the engine from various positions, while the lift is either elevated or in a lowered position.

Another object is to provide a lift with a platform that has a cutout portion through which the frame with the load support may pass, whereby the level of the load can be readily adjusted to a level suitable for working on various portions of the engine while the frame and platform are elevated.

Another object of the present invention is to provide a lift wherein the frame and load support are located adja cent one of the lateral sides of the base structure, so that the lift may be easily loaded or unloaded by means of a conventional forklift truck.

A further object of the invention is to provide a load support, which can be adjusted to various attitudes so as to align the engine properly with the wing of the airplane.

Other objects and advantages of the present invention will become more apparent after reading the following disclosure in combination with the accompanying drawings in which:

FIGURE 1 is a perspective view of the maintenance lift of the present invention;

FIGURE 2 is .a cross-sectional view of the telescoping jack assembly used to elevate the frame and platform;

FIGURE 3 is a schematic view of the control system for operating the hydraulic jacks; and

FIGURE 4 is a schematic view of the control system used to elevate and adjust the work support relative to the frame.

Detailed description of the invention As shown in FIGURE 1, the maintenance lift of the present invention comprises a rectangular base structure 10 made up of channel members 12, 13, 14 and 15 and a centrally located channel member 16 extending between channel members 12 and 14. The channel members are made of iron, steel or similar material and although, as shown, the members are welded together at their joints, it is contemplated that the joints could also be joined by means of rivets, bolts or other means well known in the art. The base frame has common swivel casters 17 mounted at the corners thereof which are well known in the prior art. These casters may be mounted on the frame in any suitable manner such as by welding plates 18 onto the bottom of the channel members.

A platform 19, which may be made of iron, steel or other similar materials, is mounted on the upper sleeves of telescoping jack assemblies 20 and 22 by means of brackets 24, 25 which are welded to the platform and the upper sleeves. The telescoping jack assemblies each have lower portions 26, which are closed at the bottom and are welded to the outer surfaces of base structure channel members 13 and 15 at the midportions of the channel members.

Platform 19 has a rectangular cutout portion defined by edges 30, 31 and 32 of the platform, which makes the platform substantially L-shaped. In the preferred form, edge extends for more than half the length of the platform and edge 31 extends for more than half the width of the platform, while edge 32 extends parallel to edge 30 from edge 31 to telescoping jack assembly 22. Due to the cutout portion and since the telescoping jack assemblies 20 and 22 are mounted on the outer surfaces of channel members 13 and 15, bracket 25 is welded to an overhanging portion 34 of platform 19.

A metallic frame 35 is also mounted on the base structure 10 by telescoping hydraulic jack assemblies 36 and 38, which are identical to the assemblies used to support the platform. Telescoping jack 36 is mounted on and welded to the upper surface of member 15 and telescoping jack 38 is mounted on and welded to the upper surface of central member 16. Telescoping jack 38 is mounted adjacent to but laterally spaced from edge 30 of platform 19 at the midportion of the edge. Telescoping jack 36 is mounted directly across from jack 38 and the outer surface of jack 36 is spaced laterally inwardly from the inner surface of jack 22 for reasons as will be explained hereinafter.

The frame 35 is rectangular with somewhat smaller outside dimensions than the cutout portion of platform 19, and is mounted at its midportion on the upper sleeves of the telescoping jack assemblies 36 and 38. The outer surfaces of lateral elements 40 and 41 of frame 35 are flush with the outer surfaces of jacks 36 and 38, respectively. Since jack 36 is spaced inwardly from jack 22 and edge 32 on one side and jack 38 is spaced laterally from edge 30 on the other side, frame 35 can pass through the cutout portion of platform 19 without interfering with the upper sleeve of jack 22 or edges 30, 32 of platform 19. With jack 38 mounted on frame member 16 at a point midway along edge 30 of the platform and with jack 36 mounted directly across from jack 38, frame 35,

which has smaller outside dimensions than the cutout portion and is mounted at its midportion on jacks 36 and 38, can be raised and lowered without interfering with edge 31 of the platform. Thus, of course, the level of frame 35, with respect to platform 19, can be adjusted so that the frame is above, below or level with the platform 19.

FIGURE 2 shows one form of the telescoping hydraulic jacks 20, 22, 36 and 38 which may be used in the present invention. The jack, as shown, is fully extended and comprises a hydraulic cylinder 50 mounted within the telescoping rectangular sleeve element 51. The upper end 58 of the driven piston 56 supports two idler pulleys 59, about which are trained cables 60, 61 anchored to lugs 62 and 63 on sleeve member 51 and anchored to lugs 64, 65 on sleeve member 53. Sleeve member 53 also has two idler pulleys 66 mounted at the upper end thereof on a shaft which is rotatably supported in the sleeve member. Cables 67, 68 are trained about pulleys 66 and are anchored to lugs 69, 70 on the sleeve member 52 and anchored to lugs 71, 72 on the sleeve member 54. The cables 60, 61, 67 and 68 are secured to the lugs by any suitable means such as by welding. The sets of lugs are laterally spaced with respect to each other, in such a manner that the cables do not interfere with each other and the upper flanges and a portion of the side walls of the telescoping sleeves are notched to permit the cables and lugs of the various sleeves to pass by the upper portions of other sleeves when the jack assembly is extended or retracted.

The pulleys 59 and 66 and the cables 60, 61 and 67, 68 act as a linear motion amplifying device so that energization of the actuator 50 to elevate the piston 56 vertically positions the telescoping jack assembly at a height above the upper portion of piston 56. As piston 56 is extended, cables 60 and 61 elevate sleeve 53. Sleeve 53 has pulleys 66 mounted therein and acts as a second piston, elevating sleeves 52 and 54 which are connected by cables 67 and 68 that are trained over pulleys 66. The interlocking flanges of the sleeve members prevent any of the sleeves from being elevated too far. The operation of the controls for actuating the hydraulic jacks will be discussed in detail hereinafter.

Rectangular frame 7 4 is mounted on frame 35 by means of four extensible hydraulic piston and cylinder assemblies 76, 77, 78 and 79, which are pivotally mounted on and extend between respective corners of the two frame members. The outside dimensions of frame 74 are smaller than the inside dimensions of frame 35 and, therefore, the extensible hydraulic piston and cylinder assemblies extend diagonally upwardly and inwardly from the corners of frame 35. Each piston and cylinder assembly is provided with lugs 80 and 81 at each extremity. Each lug 80 is mounted on the piston and is pivotally connected to a bracket 82, which is welded to the lower corner of frame 74. Each lug 81 is mounted on the cylinder and is pivotally connected to a bracket 83, which is welded to the upper surface of frame 35. A pin 85 passes through aligned apertures in each bracket and lug thereby pivotally mounting the piston and cylinder assembly on the respective frames. The piston assemblies are conventional and have inlet-exhaust ports which are connected, by hydraulic lines 86, 87, 88 and 89, to a control means 90 mounted on frame 35. The control means, in turn, is connected to a source of hydraulic fluid, under pressure, and to an exhaust reservoir. A more detailed discussion of the operation of the piston members in conjunction with the control means which co-operate so as to elevate and change the attitude of frame 7 4 will follow.

Frame 74 is made of such a width, that suflicient clearance is left between the upper sleeve members of jack assemblies 36, 38 and the frame 74 whereby movement of the frame is not restricted by the telescoping sleeves of the jacks, The frame 74 is also provided with a suitable means for receiving the engine to be handled and attached to the airplane. As shown in FIGURE 1, the cradle-like supports 92 have a concave upper surface into which the engine may be deposited by the forklift and from which the engine may be readily attached to the airplane wing.

With regard to the operation of the present invention, a control panel 94 is mounted on platform 19, which enables the operator of the lift to individually raise or lower platform 19 and frame 35. The controls may be of any suitable form well known in the art, and are arranged as diagrammatically shown in FIGURE 3.

As shown in FIGURE 3, the hydraulic fluid is pumped by pump P from a reservoir R through hydraulic line 95 into valves 96 and 97. Actuation of valve 96, as shown in FIGURE 3, places supply line 95 in communication with lines 98 and 99 permitting hydraulic fluid, under pressure, to flow to cylinders 50 of telescoping jacks 20 and 22, thereby causing the piston 56 within each assembly to move upwardly, extending the telescoping jack members. Upon movement of the valve, so that lines 98 and 99 are in communication with exhaust line 100, fluid is permitted to flow from the cylinders 50 whereby pistons 56 and the hydraulic jack assemblies 20 and 22 are lowered. The valve 96 or exhaust line 100 is provided with a restriction therein, which allows fluid to escape from the cylinder at a limited rate, thereby preventing the jack assemlies from lowering too fast. Valve 97 operates in the same manner as valve 96 whereby positioning of the valve in one position permits fluid, under pressure, to flow from supply line 95 to the respective piston and cylinder assemblies 50 of telescoping jacks 36 and 38 through hydraulic lines 101, 102 and positioning of valve 97 in another position permits fluid to flow from the hydraulic piston and cylinder assemblies through lines 101, 102 to exhaust line 100 and into the reservoir. As with valve 96, valve 97 or exhaust line 100 is provided with a restriction, which allows fluid to escape from the cylinder at a limited rate, to prevent the platforms from lowering toofast.

The control for actuating cylinders 76, 77, 78 and 79 is mounted on frame 35. However, if desired, this control could also be mounted on the platform along with the other valve members. The control 90 may be of any one of numerous valves disclosed in the prior art, and is merely shown diagrammatically in FIGURE 4 to help illustrate the manner in which the attitude and elevation of frame 74 may be controlled by the valve.

As shown in- FIGURE 4, hydraulic fluid is pumped from reservoir R through pump P to supply lines 106, 107, 108 and 109 located within the control 90. These supply lines communicate with respective valve assemblies 116, 117, 118 and 119 within the control 90, which regulate the flow of hydraulic fluid to and from piston and cylinder assemblies 76, 77, 78 and 79 through lines 86, 87, 88 and 89, respectively. The valve assemblies are all also provided with exhaust lines 126, 127, 128 and 129, which are joined to a common exhaust line 120 that leads from control 90 to the reservoir. Valve assemblies 116, 117, 118 and 119 are operated by a common lever or control stick 122 which permits each valve assembly to be actuated independently, pairs of valve assemblies to be actuated or all four valve assemblies to be actuated at the same time. This is accomplished by mounting lever 122 in a ball socket, or similar mounting, which permits the lever to be tilted at any angle with respect to the horizontal. In this way, extensions 136, 137, 138 and 139 may be tilted so that only one of the members comes in contact with a valve assembly, or so that two of the members will come in contact with two valve assemblies. By mounting the ball socket in a spring-biased sleeve or similar member, which permits reciprocal motion in the vertical direction, all the valve assemblies could be activated simultaneously by pushing directly down on the lever 122. In this way, one or two of the piston and cylinder assemblies 76, 77, 78 or 79 can be extended or retracted to change the attitude of frame 74, or all of the valves can be actuated simultaneously to elevate or lower the entire frame.

The valve assemblies 116, 117, 118 and 119, within control 90, may be of any form wherein either the supply or exhaust lines can selectively be placed in communication with the hydraulic piston and cylinder assemblies. One form that the individual valve assemblies might take is a hollow cylindrical housing with a piston therein. The piston would be spring-biased upwardly and have a central-bore therein. The cylinder would be closed at both ends and have a supply port at the upper portion thereof, an exhaust port located below the supply port and a port in the bottom which communicates with an extensible hydraulic piston and cylinder assembly. In its uppermost position, when the valve is not being actuated, the piston would cover the supply port, but the exhaust port would be uncovered permitting communication between the exhaust port and the port leading to an extensible hydraulic piston and cylinder assembly. When the piston was partially depressed, it would be of such a length that both the exhaust and supply ports would be covered by the piston. It is in this position that a suitable means can be arranged for locking the piston against axial movement, if it were desired to prevent flow to or from the hydraulic piston and cylinder assembly, Further, depression of the piston would uncover the supply port while still covering exhaust port, thereby permitting communication through the hole in the piston, between the supply lines and the hydraulic piston and cylinder assemblies. Of course, the piston would be provided with suitable sealing rings around the periphery thereof to prevent leakage of the fluid. While the preferred form of the valve has been described to illustrate the various forms in which the valve may take, it is to be understood that any valve structure of this sort could be utilized, if desired.

The present invention, as illustrated and described, utilizes hydraulic controls and hydraulic piston and cylinder assemblies. It is contemplated that pneumatic, electrical and mechanical systems or combinations thereof could also be utilized to actuate the various components of the present invention.

What is claimed is:

1. A lift comprising a mobile base structure:

a platform having a cut-out portion and being substantially L-shaped, said platform being mounted on extensible supports which are secured to said base structure;

a first rectangular frame received within said cut-out portion and mounted on extensible supports secured to said base structure;

a second rectangular frame mounted on said first frame by four extensible elements pivotally secured to and extending between respective corners of said first and second frames with the height and attitude of said second frame being adjustable with respect to said first frame by means of said extensible elements, and; load supports carried by saidsecond frame.

2. The lift of claim 1 wherein said extensible supports are telescoping jack assemblies.

3. The lift of claim 1 wherein the extensible supports are telescoping jack assemblies, the platform and first frame being secured to upper sleeves of said telescoping jack assemblies and said upper sleeves of said telescoping jack assemblies extending respectively above said platform and said first frame.

4. The lift of claim 3 wherein the platform ad the first frame are each mounted on a pair of telescoping jack assemblies and wherein a means is provided to independently actuate each pair of telescoping jack assemblies.

5. A lift comprising a mobile base structure:

a platform for carrying operating personnel, said platform having a cut-out portion and being substantially L-shaped and mounted on extensible supports which are secured to said base structure;

a first frame received within said cut-out portion and mounted on extensible supports secured to said base structure;

control means for actuating said extensible supports wherein the height of said platform and said first frame can be varied with respect to each other;

a second frame mounted on said first frame by four extensible elements pivotally mounted on and extending between spaced-apart locations on said first and second frames with the height and attitude of said second frame with respect to said first frame being adjustable by means of said four extensible elements, and;

load support means carried by said second frame.

References Cited UNITED STATES PATENTS 2,468,884 5/1949 LEsperance et al. 2 14-1 3,085,798 4/1963 Gavette 26917 2,938,595 5/1960 Miller 187-9 X 3,291,321 12/1966 Hamilton 214-1 FOREIGN PATENTS 1,378,978 10/ 1964 France.

GERALD M. FORLENZA, Primary Examiner. FRANK E. WERNER, Assistant Examiner.

US. Cl. X.R. 3 

